Construction machine

ABSTRACT

A hydraulic excavator includes: a multijoint type front implement that is configured by coupling a plurality of driven members including a bucket; inertial measurement units that detect posture information about the plurality of driven members; and a calibration value computing section that computes calibration parameters used in calibration of detection results of the inertial measurement units; and a work position computing section that computes a relative position of the bucket to the machine body on the basis of the detection results of the inertial measurement units and the computation result of the calibration value computing section, and the calibration value computing section computes the calibration parameters on the basis of the detection results of the inertial measurement units in a plurality of postures of the front implement in which a reference point set on any of the plurality of driven members in advance matches a reference position.

TECHNICAL FIELD

The present invention relates to a construction machine having a frontimplement.

BACKGROUND ART

In recent years, to respond to intelligent construction, a constructionmachine that has a machine guidance function to display a posture of awork implement having driven members such as a boom, an arm, and abucket, and a position of a work tool such as a bucket to an operator,and a machine control function to exercise control in such a manner thatthe work tool such as the bucket moves along a target work executionsurface has been put into practical use. Typical functions of thesefunctions include a function to display a position of a bucket tip endand an angle of the bucket of a hydraulic excavator on a monitor and afunction to limit an action of the hydraulic excavator in such a mannerthat a distance by which the bucket tip end approaches the target workexecution surface is equal to or smaller than a certain distance.

To realize such functions, it is necessary to compute the postures ofthe work implement, and higher precision of this posture computationenables higher-level work execution. To compute the postures of the workimplement, it is necessary to detect rotation angles of the boom, thearm, and the bucket using sensors which are, for example, potentiometersor inertial measurement units. It is also necessary to accurately graspmounting positions, angles, and the like of the sensors to realize highprecision posture computation. However, mounting errors are generated inactual operation at a time of mounting the sensors to the constructionmachine; thus, to accurately compute the postures of the work implementof the construction machine, the construction machine needs to beconfigured with calibration means of some sort to correct these errors.

Examples of a calibration method of calibrating the mounting positionsof the sensors mounted to the work implement include use of an externalmeasuring device, for example, a total station. With this method,however, it is impossible to carry out calibration work in anenvironment in which the external measuring device is unavailable (forexample, in a case in which the total station is used but a laser beamis poorly reflected in rainy weather) or at a work site where anoperator capable of handling the external measuring device is absent.Moreover, measurement using the external measuring device requiresman-hours for the measurement; thus, a calibration method without usingthe external measuring device is desired.

Examples of the calibration method without utilizing the externalmeasuring device include a technique described in, for example, PatentDocument 1. According to this technique, a construction machineconfigured with potentiometers at links of a work implement adapts aposition of a work tool (for example, a bucket claw tip) to a specificreference plane extending in a longitudinal direction and correctsvertical positions of the work tool corresponding to a plurality ofpositions in the longitudinal direction of the work tool at this time.

PRIOR ART DOCUMENT Patent Documents

Patent Document 1: JP-1995-102593-A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

The conventional technique is intended to accurately compute a height ofthe bucket at a time of grounding the bucket by correcting a height ofthe bucket claw tip with a ground or the like set as the referenceplane. However, the plurality of sensors installed in the work implementor the like exhibit inherent error characteristics different from oneanother. Owing to this, in a case in which the postures of the workimplement (angles of the boom, the arm, and the bucket) differs fromthat at a time of correction, that is, in a case, for example, in whichwork is conducted on a working surface having a shape different fromthat of the reference plane (plane) used at the time of executingcorrection, errors of the sensors change to reduce precision ofcorrection values, with the result that it is impossible to accuratelycompute the postures of the work implement.

The present invention has been achieved in the light of the aboverespects and an object of the present invention is to provide aconstruction machine capable of highly precisely computing a posture ofa work implement with a simpler configuration.

Means for Solving the Problems

The present application includes a plurality of means for solving theproblems. An example, there is provided a construction machineincluding: a multijoint type front work implement that is configured bycoupling a plurality of driven members including a work tool and that issupported by a machine body of the construction machine in such a manneras to be rotatable in a perpendicular direction; posture informationsensors that detect posture information about the plurality of drivenmembers; and a front posture computing device that computes a posture ofthe multijoint type front work implement on the basis of detectioninformation from the posture information sensors, an action of themultijoint type front work implement being controlled on the basis ofthe posture of the multijoint type front work implement computed by thefront posture computing device. The construction machine is configuredin such a manner that the front posture computing device includes: areference position setting section that sets a reference positionspecified relatively to the machine body; a calibration value computingsection that computes calibration parameters used in calibration of thedetection information from the posture information sensors; and a workposition computing section that computes a relative position of the worktool to the machine body on the basis of the detection information fromthe posture information sensors and a computation result of thecalibration value computing section. Further, the construction machineis configured in such a manner that the calibration value computingsection computes the calibration parameters on the basis of thedetection information from the posture information sensors in aplurality of postures of the front work implement in which a referencepoint set on any of the plurality of driven members in advance matchesthe reference position set by the reference position setting section,which differ in a posture of at least one of the plurality of drivenmembers, and the number of which corresponds to the number of the drivenmembers.

Advantages of the Invention

According to the present invention, it is possible to appropriatelycontrol distribution flow rates to hydraulic actuators and improveoperator's operability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an outward appearance of a hydraulicexcavator that is an example of a construction machine according toEmbodiment 1.

FIG. 2 is a schematic diagram depicting part of processing functions ofa controller on board of the hydraulic excavator.

FIG. 3 is a functional block diagram schematically depicting processingfunctions of a posture computing device in the controller.

FIG. 4 is a side view schematically depicting a relationship between afront implement coordinate system defined in Embodiment 1 and thehydraulic excavator.

FIG. 5 is a diagram depicting an example of a posture of a frontimplement in a case of capturing posture angles.

FIG. 6 is a diagram depicting an example of the posture of the frontimplement in the case of capturing posture angles.

FIG. 7 is a diagram depicting an example of the posture of the frontimplement in the case of capturing posture angles.

FIG. 8 is a flowchart depicting a posture computation process accordingto Embodiment 1.

FIG. 9 is a functional block diagram schematically depicting processingfunctions of a posture computing device in the controller according to amodification of Embodiment 1.

FIG. 10 is a diagram depicting an example of a relationship between areference plane and the posture of the front implement in the case ofcapturing the posture angles.

FIG. 11 is a diagram depicting an example of a relationship between thereference plane and the posture of the front implement in the case ofcapturing the posture angles.

FIG. 12 is a diagram depicting an example of a relationship between thereference plane and the posture of the front implement in the case ofcapturing the posture angles.

FIG. 13 is a diagram depicting an example of a relationship between thereference plane and the posture of the front implement in the case ofcapturing the posture angles.

FIG. 14 is a side view schematically depicting a relationship between afront implement coordinate system and a hydraulic excavator according toEmbodiment 2.

FIG. 15 is a flowchart depicting a posture computation process accordingto Embodiment 3.

FIG. 16 is a diagram depicting an example of a posture of a bucket withrespect to the reference plane.

FIG. 17 is a diagram depicting an example of the posture of the bucketwith respect to the reference plane.

FIG. 18 is a diagram depicting an example of the posture of the bucketwith respect to the reference plane.

FIG. 19 is a diagram depicting an example of the posture of the bucketwith respect to the reference plane.

FIG. 20 is a flowchart depicting a posture computation process accordingto Embodiment 4.

FIG. 21 is a diagram depicting a posture with a boom tip end adapted tothe reference plane.

FIG. 22 is a diagram depicting a posture with an arm tip end adapted tothe reference plane.

FIG. 23 is a diagram depicting a posture with a bucket tip end adaptedto the reference plane.

FIG. 24 is a diagram depicting a calibration table of calibrationparameters linearly interpolated in each section.

FIG. 25 is a diagram depicting a calibration table of smoothing thecalibration parameters in all possible angle sections.

FIG. 26 is a diagram depicting a boom, an arm, and a bucket of ahydraulic excavator according to a conventional technique by athree-link mechanism, schematically depicting coordinates of a claw tipposition of the bucket from an origin of a front implement coordinatesystem, and depicting work of forming a level.

FIG. 27 is a diagram depicting the boom, the arm, and the bucket of thehydraulic excavator according to the conventional technique by thethree-link mechanism, schematically depicting the coordinates of theclaw tip position of the bucket from the origin of the front implementcoordinate system, and depicting work of forming a slope such as a faceof slope.

MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinafter withreference to the drawings. In the present embodiments, a hydraulicexcavator configured with a bucket as a work tool on a tip end of afront implement (front work implement) will be described by way ofexample of a construction machine. However, the present invention isalso applicable to a hydraulic excavator configured with an attachmentsuch as a breaker or a magnet other than the bucket.

Embodiment 1

Embodiment 1 of the present invention will be described with referenceto FIGS. 1 to 8.

FIG. 1 is a schematic diagram of an outward appearance of the hydraulicexcavator that is an example of a construction machine according toEmbodiment 1.

In FIG. 1, a hydraulic excavator 100 is configured with a multijointtype front implement (front work implement) 1 configured by coupling aplurality of driven members (a boom 4, an arm 5, and a bucket (worktool) 6) rotating in a perpendicular direction, and an upper swingstructure 2 and a lower travel structure 3 configuring a machine body,and the upper swing structure 2 is provided swingably with respect tothe lower travel structure 3. Furthermore, a base end of the boom 4 ofthe front implement 1 is supported by a front portion of the upper swingstructure 2 in such a manner as to be rotatable in the perpendiculardirection, one end of the arm 5 is supported by an end portion (tip end)other than the base end of the boom 4 in such a manner as to berotatable in the perpendicular direction, and the bucket 6 is supportedby the other end of the arm 5 in such a manner as to be rotatable in theperpendicular direction. The boom 4, the arm 5, the bucket 6, the upperswing structure 2, and the lower travel structure 3 are driven by a boomcylinder 4 a, an arm cylinder 5 a, a bucket cylinder 6 a, a swing motor2 a, and left and right travel motors 3 a (only one of which isdepicted), respectively.

The boom 4, the arm 5, and the bucket 6 act on a plane including thefront implement 1, and this plane is often referred to as “actionplane,” hereinafter. In other words, the action plane is a planeorthogonal to rotational axes of the boom 4, the arm 5, and the bucket6, and can be set at a center in width directions of the boom 4, the arm5, and the bucket 6.

Operation levers (operation devices) 9 a and 9 b that output operationsignals for operating the hydraulic actuators 2 a to 6 a are provided ina cabin 9 of which an operator is on board. Although not depicted inFIG. 1, the operation levers 9 a and 9 b are tiltable longitudinally andhorizontally, include sensors, not depicted, electrically detectinglever tilt amounts, that is, lever operation amounts that are theoperation signals, and output the lever operation amounts detected bythe sensors to a controller 19 (refer to FIG. 2) via electricinterconnections. In other words, operating the hydraulic actuator 2 ato 6 a is allocated to longitudinal or horizontal directions of theoperation levers 9 a and 9 b.

Actions of the boom cylinder 4 a, the arm cylinder 5 a, the bucketcylinder 6 a, the swing motor 2 a, and the left and right travel motors3 a are controlled by causing a control valve 8 to control directionsand flow rates of hydraulic working fluids supplied to the hydraulicactuators 2 a to 6 a from a hydraulic pump device 7 driven by a primemover such as an engine or an electric motor which is not depicted. Thecontrol valve 8 is based on a drive signal (pilot pressure) output froma pilot pump, not depicted, via solenoid proportional valves. Thecontroller 19 controls the solenoid proportional valves on the basis ofthe operation signals from the operation levers 9 a and 9 b, therebycontrolling the actions of the hydraulic actuators 2 a to 6 a.

It is noted that the operation levers 9 a and 9 b may be hydraulic pilottype operation levers, and may be configured to supply pilot pressuresin response to operation directions and operation amounts of theoperation levers 9 a and 9 b operated by an operator to the controlvalve 8 as drive signals, and to drive the hydraulic actuators 2 a to 6a.

Inertial measurement units (IMU) 12 and 14 to 16 are disposed in theupper swing structure 2, the boom 4, the arm 5, and the bucket 6 asposture sensors, respectively. In a case in which it is necessary todistinguish these inertial measurement units, the inertial measurementunits will be referred to as “machine body inertial measurement unit12,” “boom inertial measurement unit 14,” “arm inertial measurement unit15,” and “bucket inertial measuring device 16.”

The inertial measurement units 12 and 14 to 16 measure angularvelocities and accelerations. If considering a case in which the upperswing structure 2 and the driven members 4 to 6 in which the inertialmeasurement units 12 and 14 to 16 are disposed are at a standstill, itis possible to detect directions (postures: posture angles θ to bedescribed later) of the upper swing structure 2 and the driven members 4to 6 on the basis of directions of gravitational accelerations (that is,vertically downward directions) in IMU coordinate systems set to theinertial measurement units 12 and 14 to 16 and mounting states of theinertial measurement units 12 and 14 to 16 (that is, relative positionrelationships between the inertial measurement units 12 and 14 to 16 andthe upper swing structure 2 and the driven members 4 to 6). Here, theinertial measurement units 14 to 16 configure posture informationsensors that detect information about respective postures of theplurality of driven members (hereinafter, referred to as “postureinformation”).

It is noted that the posture information sensors are not limited to theinertial measurement units but that tilting angle sensors, for example,may be used as the posture information sensors. Alternatively,potentiometers may be disposed in coupling portions of coupling thedriven members 4 to 6 to detect relative directions of (postureinformation about) the upper swing structure 2 and the driven members 4to 6 and to obtain the postures of the driven members 4 to 6 fromdetection results. In another alternative, stroke sensors may bedisposed in the boom cylinder 4 a, the arm cylinder 5 a, and the bucketcylinder 6 a and configured to calculate relative directions of (postureinformation about) connection portions of connecting the upper swingstructure 2 and the driven members 4 to 6 from amounts of change instroke, and to obtain the postures (posture angles θ) of the drivenmembers 4 to 6 from calculation results.

FIG. 2 is a schematic diagram depicting part of processing functions ofthe controller on board of the hydraulic excavator.

In FIG. 2, the controller 19 has various functions to control theactions of the hydraulic excavator 100, and part of the variousfunctions include a posture computing device 15 a, a monitor displaycontrol system 15 b, a hydraulic system control system 15 c, and a workexecution target surface computing device 15 d.

The posture computing device 15 a performs a posture computation process(to be described later) for computing a posture of the front implement 1on the basis of detection results from the inertial measurement units 12and 14 to 16 and an input from a computation posture setting section 18(to be described later) disposed in the cabin 9.

The work execution target surface computing device 15 d computes a workexecution target surface defining a target shape of an object to beworked on the basis of work execution information 17 such as athree-dimensional working drawing stored in a storage device, notdepicted, by a work manager and the posture of the front implement 1computed by the posture computing device 15 a.

The monitor display control system 15 b, which controls display of amonitor provided in the cabin 9 and which is not depicted, computes aninstruction content of operation support for the operator on the basisof the work execution target surface computed by the work executiontarget surface computing device 15 d and the posture of the frontimplement 1 computed by the posture computing device 15 a, and displaysthe instruction content on the monitor of the cabin 9. In other words,the monitor display control system 15 b plays part of functions as amachine guidance system that supports operator's operation by, forexample, displaying on the monitor the posture of the front implement 1having the driven members such as the boom 4, the arm 5, and the bucket6 and a tip end position and an angle of the bucket 6.

The hydraulic system control system 15 c, which controls a hydraulicsystem for the hydraulic excavator 100 configured with the hydraulicpump device 7, the control valve 8, and the hydraulic actuators 2 a to 6a, computes the actions of the front implement 1 on the basis of thework execution target surface computed by the work execution targetsurface computing device 15 d and the posture of the front implement 1computed by the posture computing device 15 a, and controls thehydraulic system for the hydraulic excavator 100 to realize the actionsof the front implement 1. In other words, the hydraulic system controlsystem 15 c plays part of functions as a machine control system thatlimits the actions in such a manner, for example, that a distance bywhich a tip end of the work tool such as the bucket 6 approaches thework execution target surface does not exceed a certain distance andthat the work tool (for example, a claw tip of the bucket 6) moves alongthe work execution target surface.

FIG. 3 is a functional block diagram schematically depicting processingfunctions of the posture computing device in the controller. Inaddition, FIG. 4 is a side view schematically depicting a relationshipbetween a front implement coordinate system defined in Embodiment 1 andthe hydraulic excavator.

In FIG. 3, the posture computing device 15 a performs the posturecomputation process for computing the posture of the front implement 1on the basis of the detection results from the inertial measurementunits 12 and 14 to 16 and the input from the computation posture settingsection 18 disposed in the cabin 9, and has functional sections such asa design information storage section 151, a reference plane settingsection 152, a calibration value computing section 153, and a workposition computing section 154.

The design information storage section 151 is a storage device such as aROM (Read Only Memory) or a RAM (Random Access Memory) to whichinformation about machine body dimensions of the construction machine iswritten. Examples of the machine body dimensions stored in the designinformation storage section 151 include a width (machine body width) anda length of the upper swing structure 2, a swing central position of theupper swing structure 2, a mounting position of the front implement 1 atwhich the front implement 1 is mounted to the upper swing structure 2(that is, a position of a boom foot pin) and lengths of the boom 4, thearm 5, and the bucket 6.

The reference plane setting section 152 sets a reference plane used in aparameter calibration process (to be described later) performed by thecalibration value computing section 153 on the basis of the machine bodydimensions obtained from the design information storage section 151.

The reference plane set by the reference plane setting section 152, thedetection results of the boom inertial measurement unit 14, the arminertial measurement unit 15, and the bucket inertial measuring device16, and a computation result of the work position computing section 154are input to the calibration value computing section 153, and thecalibration value computing section 153 computes calibration parametersfor calibrating the detection results from the inertial measurementunits 14 to 16.

The work position computing section 154 computes a relative position ofthe work tool provided on the tip end of the front implement 1 (claw tipposition of the bucket 6 in Embodiment 1) with respect to the machinebody on the basis of the detection results from the inertial measurementunits 12 and 14 to 16 and a computation result of the calibration valuecomputing section 153.

A principle of the posture computation process will now be described.

As depicted in FIG. 4, in Embodiment 1, a front implement coordinatesystem that is an orthogonal coordinate system defining an x-axis in alongitudinal direction of the upper swing structure 2 (positive in aforward direction) and a z-axis in a vertical direction (positive in anupward direction) with the position of the boom foot pin (that is, arotation center of the boom 4 with respect to the upper swing structure2) assumed as an origin O (0, 0) is used. In other words, the frontimplement coordinate system is set on the action plane of the frontimplement 1.

If it is assumed that a distance between a rotation fulcrum of the boom4 (position of the boom foot pin) and a rotation fulcrum of the arm 5(coupling portion of coupling the boom 4 and the arm 5) is a boom lengthL_(bm), a distance between the rotation fulcrum of the arm 5 and arotation fulcrum of the bucket 6 (coupling portion of coupling the arm 5and the bucket 6) is an arm length L_(am), and a distance between therotation fulcrum of the bucket 6 and a reference point B of the bucket 6(which illustrates a case of setting the tip end (claw tip) of thebucket 6 as the reference point B in advance) is a bucket length L_(bk),then coordinate values (x, z) of the reference point B in the frontimplement coordinate system can be obtained from the following Equations(1) and (2), where angles (posture angles) formed between the boom 4,the arm 5, and the bucket 6 (to be precise, directions of the boomlength L_(bm), the arm length L_(am), and the bucket length L_(bk)) anda horizontal direction are θ_(bm), θ_(am), and θ_(bk), respectively.[Equation 1]x=L _(bm) cos(θ_(bm)−θ_(bm) ^(s))+L _(am) cos(θ_(am)−θ_(am) ^(s))+L_(bk) cos(θ_(bk)−θ_(bk) ^(s)  (1)[Equation 2]x=L _(bm) sin(θ_(bm)−θ_(bm) ^(s))+L _(am) sin(θ_(am)−θ_(am) ^(s))+L_(bk) sin(θ_(bk)−θ_(bk) ^(s))   (2)

It is noted that the posture angles θ_(bm), θ_(am), and θ_(bk) indicatepositive values above the horizontal direction and negative values belowthe horizontal direction.

Here, θ^(s) is a calibration parameter and can be obtained from thefollowing Equation (3), where a true value of each posture angle isθ^(t), on the basis of assumption that the posture angles θ (θ_(bm),θ_(am), and θ_(bk)) detected by the posture information sensors(inertial measurement units 14 to 16 in Embodiment 1) or the postureangles θ computed from the posture information have offset errors.[Equation 3]θ^(t)=θ+θ^(s)   (3)

In Equations (1) and (2), the calibration parameters are defined asθ^(s) _(bm), θ^(s) _(am), and θ^(s) _(bk) to correspond to the postureangles θ_(bm), θ_(am), and θ_(bk), respectively.

The calibration value computing section 153 computes the calibrationparameters θ^(s) _(bm), θ^(s) _(am), and θ^(s) _(bk) on the basis ofEquation (2). Specifically, a known value of z is set to a left side ofEquation (2) and the detection results (posture angles θ_(bm), θ_(am),and θ_(bk)) from the inertial measurement units 14 to 16 (postureinformation sensors) are set to a right side of Equation (2) bydisposing the reference point of the work tool of the front implement 1(here, the reference point B set to the claw tip of the bucket 6) on thereference plane (set by the reference plane setting section 152) towhich the known value of z is given, whereby the calibration valuecomputing section 153 computes the calibration parameters θ^(s) _(bm),θ^(s) _(am), and θ^(s) _(bk). Since the lengths that are the boom lengthL_(bm), the arm length L_(am), and the bucket length L_(bk) do notgreatly change during short-time work, values given by the designinformation storage section 151 are handled as constants.

In a case of setting the position (height) of the reference point B tothe known value z_(set), Equation (2) can be expressed by the followingEquation (4).[Equation 4]z _(set) =L _(bm) sin(θ_(bm)−θ^(s) _(bm))+L _(am) sin(θ_(am)−θ^(s)_(am))+L _(bk) sin(θ_(bk)−θ^(s) _(bk))   (4)

In Equation (4), the number of unknown variables is three, that is, theunknown variables are the calibration parameters θ^(s) _(bm), θ^(s)_(am), and θ^(s) _(bk), and the number is equal to the number ofinertial measurement units 14 to 16 disposed in the plurality of drivenmembers 4 to 6. Therefore, if at least three simultaneous equationsdifferent in at least one of the posture angles θ_(bm), θ_(am), andθ_(bk) in Equation (4) can be set up, the calibration parameters θ^(s)_(bm), θ^(s) _(am), and θ^(s) _(bk) can be determined.

It is noted that even in a case in which the number of driven members isequal to or larger than four (in other words, the number of calibrationparameters is equal to or larger than four), those calibrationparameters can be determined if simultaneous equations as many as thedriven members configuring the front implement 1 can be set up.

(Setting of Reference Plane: Reference Plane Setting Section 152)

In Embodiment 1, a case of assuming a ground as the reference plane willbe given by way of example, as depicted in FIG. 4 in a case of disposingthe hydraulic excavator 100 on the substantially leveled ground. Whenthe reference point B of the bucket 6 is disposed on and caused to matchthis reference plane, the height of the reference point B corresponds toa position lower than the origin O by a height of the boom foot pin;thus, the following Equation (5) is established.[Equation 5]z _(set) =−Hp   (5)

Setting the reference plane in this way makes it possible to create thereference plane without using a special tool. While precision ofEquation (5) is possibly reduced in a case in which the ground isirregular, it is possible to ensure the precision of Equation (5) andrealize more effective computation of the calibration parameters bysetting a ground paved with concrete, an iron plate, or the like as thereference plane.

(Capture of Posture Angles θ_(bm), θ_(am), and θ_(bk): Calibration ValueComputing Section 153)

FIGS. 5 to 7 depict examples of the posture of the front implement in acase of capturing the posture angles. FIG. 5 depicts a state ofdisposing the reference point B of the bucket 6 on the reference plane(ground) in a state in which the arm 5 has sufficient operation rangesin crowding and dumping directions, FIG. 6 depicts a state of disposingthe reference point B of the bucket 6 on the reference plane (ground) ina state in which crowding of the arm 5 is greater than that in the casedepicted in FIG. 5, and FIG. 7 depicts a state of disposing thereference point B of the bucket 6 on the reference plane (ground) in astate in which dumping of the arm 5 is greater than that in the casedepicted in FIG. 5.

The posture in which the calibration parameters θ^(s) _(bm), θ^(s)_(am), and θ^(s) _(bk) are computed is set (that is, the posture anglesθ_(bm), θ_(am), and θ_(bk) are captured) by operator's operating thecomputation posture setting section 18 provided in the cabin 9. It isnoted that the computation posture setting section 18 is realized by,for example, one of functions of a switch provided in the cabin 9 or aGUI (Graphical User Interface) that functions integrally with a displaydevice such as the monitor. Furthermore, lever operation interlockedwith an action of the calibration value computing section 153 (forexample, pulling a trigger in a case of a trigger lever device) may beset as an opportunity of capture, or the posture angles θ_(bm), θ_(am),and θ_(bk) may be automatically captured in a case in which the lever isnot operated for certain time after the posture is taken for capturingthe posture angles θ_(bm), θ_(am), and θ_(bk).

As depicted in FIGS. 5 to 7, capturing the posture angles θ_(bm),θ_(am), and θ_(bk) in a plurality of postures of the front implement 1that differ in the posture of at least one of the plurality of drivenmembers 4 to 6 makes it possible to set up three simultaneous equationsin which at least one of the posture angles θ_(bm), θ_(am), and θ_(bk)different in at least one of the posture angles θ_(bm), θ_(am), andθ_(bk). Needless to say, capturing the posture angles θ_(bm), θ_(am),and θ_(bk) while the upper swing structure 2 is swung without changingthe posture of the front implement 1 is handled as one posture.

It is considered that the posture of the front implement 1 as depictedin FIGS. 5 to 7 is influenced by errors in sensor characteristics of theinertial measurement units 14 to 16 or errors in a ground state.Therefore, the posture computing device 15 a may be configured such thatwith the front implement 1 taking yet another posture, simultaneousequations more than the calibration parameters θ^(s) _(bm), θ^(s) _(am),and θ^(s) _(bk) are set up to perform computation, and the calibrationparameters θ^(s) _(bm), θ^(s) _(am), and θ^(s) _(bk) are computed by,for example, a method of least squares.

FIG. 8 is a flowchart depicting the posture computation process.

In FIG. 8, first, in a state of determining the posture of the frontimplement 1 (for example, any of the states of FIGS. 5 to 7), thereference point B of the work tool (bucket 6) is adapted to thereference plane (Step S100). By operating the computation posturesetting section 18 in this state, the posture angles θ_(bm), θ_(am), andθ_(bk) are captured as posture data in this posture and stored in thestorage section, not depicted, in the calibration value computingsection 153 (Step 110). Next, it is determined whether the posture datahas been acquired in equal to or larger than three types of postures ofthe front implement 1 (Step S120). In a case in which a determinationresult is NO, the posture of the front implement 1 is changed to anotherposture in which posture data is not acquired yet (Step S140) andprocesses in Steps S100 and S110 are repeated. Furthermore, in a case inwhich the determination result of Step S120 is YES, it is determinedwhether to end posture data acquisition (Step S130). This determinationmay correspond to a case of displaying a screen on the display devicesuch as the monitor in the cabin 9 to determine whether to continueacquiring the posture data and operator's operating the computationposture setting section 18 on an as-needed basis. Alternatively, theposture computing device 15 a may be configured to set the number oftimes equal to or larger than four (that is, larger than the number ofthe calibration parameters θ^(s) _(bm), θ^(s) _(am), and θ^(s) _(bk) asthe unknown variables) in advance and to determine whether the number oftimes is satisfied. In a case in which a determination result of StepS130 is NO, processes of Steps S140, S100, and S110 are repeated.Furthermore, in a case in which the determination result of Step S130 isYES, then simultaneous equations related to Equation (4) are set upusing the obtained posture angles θ_(bm), θ_(am), and θ_(bk), thecalibration parameters θ^(s) _(bm), θ^(s) _(am) and θ^(s) _(bk) arecomputed and stored in the calibration value computing section 153, acomputation result is output to the work position computing section 154(Step S150), and the process is ended.

Advantages of Embodiment 1 configured as described above will bedescribed while comparing the advantages with those of the conventionaltechnique.

FIGS. 26 and 27 are diagrams depicting the boom, the arm, and the bucketof the hydraulic excavator according to the conventional technique by athree-link mechanism, and schematically depicting coordinates of theclaw tip position of the bucket from the origin of the front implementcoordinate system (defined as the position of the boom foot pin). FIG.26 depicts work of forming a level and FIG. 27 depicts work of forming aslope such as a face of slope.

As can be understood from FIGS. 26 and 27, the position of the work toolwith respect to a swing longitudinal direction is equally x=L in eachwork; however, the position of the work tool with respect to thevertical direction is y=−H in the work of FIG. 26 and y=−h in the workof FIG. 27 and the position differs in value between the work of FIG. 26and that of FIG. 27. The conventional technique is intended toaccurately compute the height of the bucket at the time of grounding thebucket by correcting the height of the bucket claw tip with the groundor the like assumed as the reference plane. A plurality of sensorsinstalled in the work implement exhibit inherent error characteristicsdifferent from one another. Therefore, in a case of carrying out work ona surface at a different slope from that of the surface after makingcorrection as depicted in FIG. 27, the posture of the front implement(angles of the boom, the arm, and the bucket) differs from that at thetime of calibration; thus, a correction amount in the vertical directionnaturally differs from that at the time of calibration. The conventionaltechnique, however, is incapable of handling the case in which theposture of the work implement (angles of the boom, the arm, and thebucket) differs from that at the time of correction. In other words, ina case, for example, in which work is carried out on a working surfacehaving a shape different from that of the reference plane (plane) usedat the time of executing correction, errors of the sensors change toreduce the precision of correction values, with the result that it isimpossible to accurately compute the posture of the work implement.

In Embodiment 1, by contrast, the hydraulic excavator 100 includes: themultijoint type front implement 1 that is configured by coupling theplurality of driven members (the boom 4, the arm 5, and the bucket 6)including the bucket 6 and that is supported by the upper swingstructure 2 of the hydraulic excavator 100 in such a manner as to berotatable in the perpendicular direction; the inertial measurement units14 to 16 that detect posture information about the plurality of drivenmembers 4 to 6, respectively; and the posture computing device 15 a thatcomputes the posture of the multijoint type front implement 1 on thebasis of the detection results of the inertial measurement units 14 to16, and controls the action of the multijoint type front implement 1 onthe basis of the posture of the multijoint type front implement 1computed by the posture computing device 15 a, and the hydraulicexcavator 100 is configured in such a manner that the posture computingdevice 15 a includes the reference plane setting section 152 that setsthe reference plane specified relatively to the upper swing structure 2;the calibration value computing section 153 that computes thecalibration parameters θ^(s) _(bm), θ^(s) _(am), and θ^(s) _(bk) used incalibration of the detection results of the inertial measurement units14 to 16; and the work position computing section 154 that computes therelative position of the bucket 6 to the upper swing structure 2 on thebasis of the detection results of the inertial measurement units 14 to16 and the computation result of the calibration value computing section153, and that the calibration value computing section 153 computes thecalibration parameters on the basis of the detection results of theinertial measurement units 14 to 16 in the plurality of postures of thefront implement 1 in which the reference point set on any of theplurality of driven members 4 to 6 in advance matches the referenceplane, which differ in the posture of at least one of the plurality ofdriven members 4 to 6, and the number of which corresponds to the numberof the driven members 4 to 6. Therefore, it is possible to highlyprecisely compute the posture of the work implement with the simplerconfiguration.

In Embodiment 1, the hydraulic excavator 100 is configured in such amanner as to set the reference plane for which a value in a z-axisdirection is known, and to compute the calibration parameters θ^(s)_(bm), θ^(s) _(am), and θ^(s) _(bk) using Equation (2) for the z-axisdirection. However, the present invention is not limited to thisconfiguration and the hydraulic excavator 100 may be configured, forexample, in such a manner as to set the reference plane for which avalue in an x-axis direction is known and to compute the calibrationparameters θ^(s) _(bm), θ^(s) _(am), and θ^(s) _(bk) using Equation (1)for the x-axis direction. In another alternative, the hydraulicexcavator 100 may be configured in such a manner as to set the referenceposition for which values in the z-axis and x-axis directions are knownand to compute the calibration parameters θ^(s) _(bm), θ^(s) _(am), andθ^(s) _(bk) using Equations (1) and (2).

Modification of Embodiment 1

A modification of Embodiment 1 will be described with reference to FIG.9.

FIG. 9 is a functional block diagram schematically depicting processingfunctions of a posture computing device in the controller according tothe present modification. In FIG. 9, similar members to those inEmbodiment 1 are denoted by the same reference symbols and descriptionthereof will be omitted.

The present modification illustrates a case of disposing the designinformation storage section outside of the posture computing device. Inthe present modification, as depicted in FIG. 9, a design informationstorage section 151 a is disposed outside of a posture computing device15A, and the reference plane setting section 152, the calibration valuecomputing section 153, and the work position computing section 154acquire design information from the posture computing device 15A. Theother configurations are similar to those in Embodiment 1.

The present modification configured as described above can obtainsimilar advantages to those of Embodiment 1.

Furthermore, the present modification is suitable for changing thedesign information by replacing the design information storage section151 a in a case in which the height of the boom foot pin has changed byreplacing crawler belts of the lower travel structure 3 or a case inwhich the arm length has changed by replacing the arm by an arm ofspecial specifications.

Another modification of Embodiment 1

Another modification of Embodiment 1 will be described with reference toFIGS. 10 to 13.

In the present modification, a method of setting z_(set) is changed fromthat in Embodiment 1.

FIGS. 10 to 13 are diagrams each depicting an example of a relationshipbetween the reference plane and the posture of the front implement inthe case of capturing the posture angles.

For example, as depicted in FIG. 10, the posture angles θ_(bm), θ_(am),and θ_(bk) may be captured in a state in which a weighted string 20(so-called plumb bob) at a length H1 is mounted to the claw tip of thebucket 6 (that is, the reference point B), the plumb bob 20 completelyextends vertically, and a tip end (lower end) of the plumb bob 20 comesin contact with the ground, that is, the tip end (lower end) matches thereference plane. The weighted string 20 is a reference point relativeindex that indicates a position apart from the reference point B by apreset distance H1 in a vertically downward direction.

Since the claw tip position (reference point B) is a position higherthan the ground (reference plane) by H1 at this time, the followingEquation (6) is established.[Equation 6]z _(set) =H1−Hp   (6)

The present modification can compute the calibration parameters θ^(s)_(bm), θ^(s) _(am), and θ^(s) _(bk) more effectively since the frontimplement 1 can take more postures by changing the length of theweighted string 20. In this case, similarly to Embodiment 1, the postureof the front implement is influenced by irregularities of the ground;thus, it is preferable to capture the posture angles θ_(bm), θ_(am), andθ_(bk) while the ground paved with the concrete, the iron plate, or thelike is assumed as the reference plane.

Moreover, as depicted in FIG. 11, the posture angles θ_(bm), θ_(am), andθ_(bk) may be captured in a state in which a laser emitter 21 isprovided at a position of a height of the boom foot pin, a laser beam 21a extending in the horizontal direction with respect to the height ofthe boom foot pin is assumed as the reference plane, and the claw tipposition (reference point B) matches the reference plane. The laseremitter 21 is a reference plane index that visually indicates theposition of the reference plane by the laser beam 21 a.

Since the claw tip position (reference point B) is identical to theheight of the boom foot pin (that is, height of the origin O of thefront implement coordinate system) at this time, the following Equation(7) is established.[Equation 7]z_(set)=0   (7)

The present modification has an advantage in that no irregularities aregenerated on the reference plane, unlike the case of assuming the groundas the reference plane.

As depicted in FIG. 12, the posture angles θ_(bm), θ_(am), and θ_(bk)may be captured in a state in which a plumb bob 22 at a length H2 ismounted to the claw tip of the bucket 6 (that is, the reference pointB), the plumb bob 22 completely extends vertically, and a tip end (lowerend) of the plumb bob 22 matches the reference plane (laser beam 21 a).

Since the claw tip position (reference point B) is the position higherthan the height of the boom foot pin (that is, height of the origin O ofthe front implement coordinate system) by H2 at this time, the followingEquation (8) is established.[Equation 8]z_(set)=H2   (8)

A mounting position of the laser emitter 21 can be set to an arbitraryheight from the height of the boom foot pin. In this case, a mountingheight of the laser emitter 21 from the boom foot pin (origin O of thefront implement coordinate system) may be added to the right side ofEquation (7) or (8).

Moreover, as depicted in FIG. 13, the posture angles θ_(bm), θ_(am), andθ_(bk) may be captured in a state in which a leveling line 23 isstretched horizontally between reference members 23 a and 23 b at aposition lower than the position of the height of the boom foot pin by apreset height, and the claw tip position (reference point B) matchesthis leveling line 23 assumed as the reference plane.

Since the position of the reference plane (leveling line 23) and theclaw tip position (reference point B) are the position lower than theorigin O of the front implement coordinate system by H3 at this time,the following Equation (9) is established.[Equation 9]z _(set) =−H3   (9)

The present modification has similarly an advantage in that noirregularities are generated on the reference plane, unlike the case ofassuming the ground as the reference plane.

Embodiment 2

Embodiment 2 will be described with reference to FIG. 14.

In Embodiment 2, a case of disposing the hydraulic excavator 100according to Embodiment 1 on a sloping surface and assuming this slopingsurface as the reference plane will be given by way of example.

FIG. 14 is a side view schematically depicting a relationship between afront implement coordinate system defined in Embodiment 2 and thehydraulic excavator. In FIG. 14, similar members to those in Embodiment1 are denoted by the same reference symbols and description thereof willbe omitted.

As depicted in FIG. 14, in a case in which the hydraulic excavator 100is disposed on a sloping surface sloping by θ_(slope) in such a manneras to be higher toward a front of the upper swing structure 2 (that is,toward the front implement 1), and in which the reference plane settingsection 152 (sloping reference plane computing section) sets thissloping surface as the reference plane, the front implement coordinatesystem rotates by θ_(slope) about the origin O, compared with a case ofsetting the generally level ground as the reference plane. At this time,the direction of the gravitational accelerations detected by theinertial measurement units 14 to 16 (that is, vertically downwarddirection) also rotates by (−θ_(slope)), the coordinates of the frontimplement coordinate system are adjusted by the following Equation (10)for Equations (2) and (3) for giving the reference point B in the frontimplement coordinate system using a slope θ_(slope) of the upper swingstructure 2 (machine body) measured by the machine body inertialmeasurement unit 12.

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack & \; \\{\begin{bmatrix}{x\; 1} \\{z\; 1}\end{bmatrix} = {\begin{bmatrix}{\cos\;\theta_{slope}} & {{- \sin}\;\theta_{slope}} \\{\sin\;\theta_{slope}} & {\cos\;\theta_{slope}}\end{bmatrix}\begin{bmatrix}x \\z\end{bmatrix}}} & (10)\end{matrix}$

In Equation (10), it is assumed herein that coordinates of the frontimplement coordinate system before adjustment are (x, y) and coordinatesof the front implement coordinate system after adjustment are (x1, y1).

The other configurations are similar to those in Embodiment 1.

Embodiment 2 configured as described above can obtain similar effects tothose of Embodiment 1.

Furthermore, even in a case of disposing the hydraulic excavator 100 onthe sloping surface and carrying out work, it is possible to compute thecalibration parameters θ^(s) _(bm), θ^(s) _(am), and θ^(s) _(bk), and tocarry out the work by appropriately calculating the claw tip position ofthe bucket 6 (reference point B) in the front implement coordinatesystem.

Embodiment 3

Embodiment 3 will be described with reference to FIGS. 15 to 19.

In Embodiment 3, in a state in which causing the driven member to whichone of the plurality of calibration parameters θ^(s) _(bm), θ^(s) _(am),and θ^(s) _(bk) corresponds to take a posture in which the correspondingcalibration parameter θ^(s) can be estimated to be close to 0 (that is,a posture in which an error is considered to be difficult to generate),the calibration parameters θ^(s) of the other driven members arecomputed, and the calibration parameter θ^(s) of the one driven memberwhich is not computed is then computed, thereby enhancing the precisionof the calibration parameters θ^(s).

FIG. 15 is a flowchart depicting the posture computation processaccording to Embodiment 3. In addition, FIGS. 16 to 19 are diagrams eachdepicting an example of the posture of the bucket with respect to thereference plane.

In FIG. 15, first, the bucket 6 takes a bucket end posture in which thebucket cylinder 6 a completely extends or completely contracts (StepS200). It is noted that the posture of the bucket 6 at this time may bethe posture in which the calibration parameter θ^(s) _(bk) can beestimated to be close to zero (that is, the posture in which an error isconsidered to be difficult to generate).

By adapting the reference point B of the work tool (bucket 6) to thereference plane and operating the computation posture setting section 18in this state, the posture angles θ_(bm) and θ_(am) are captured as theposture data in this posture and stored in the storage section, notdepicted, in the calibration value computing section 153 (S210). If theposture angle of the bucket 6 in the bucket end posture is assumed asθ^(end) _(bk), the height of the reference point B in the frontimplement coordinate system is given by the following Equation (11).[Equation 11]z _(set) =L _(bm) sin(θ_(bm)−θ^(s) _(bm))+L _(am) sin(θ_(am)−θ^(s)_(am))+L _(bk) sin (θ_(bk) ^(end))   (11)

Next, it is determined whether the posture data has been acquired inequal to or larger than two types of postures of the front implement 1(Step S220). In a case in which a determination result is NO, thepostures of the boom 4 and the arm 5 of the front implement 1 arechanged to other postures in which posture data is not acquired yetwhile the bucket end posture is kept (Step S211) and processes in StepsS210 and S220 are repeated. Furthermore, in a case in which thedetermination result of Step S220 is YES, it is determined whether toend posture data acquisition (Step S230). In a case in which adetermination result of Step S230 is NO, processes of Steps S211 andS210 are repeated. Furthermore, in a case in which the determinationresult of Step S230 is YES, then simultaneous equations related toEquation (10) are set up using the obtained posture angles θ_(bm) andθ_(am) and the posture angle θ^(end) _(bk), the calibration parametersθ^(s) _(bm) and θ^(s) _(am) are computed and stored in the calibrationvalue computing section 153, and a computation result is output to thework position computing section 154 (Step S240).

Next, by changing the posture of the front implement 1 including thebucket 6 (Step S250), adapting the reference point B of the work tool(bucket 6) to the reference plane, and operating the computation posturesetting section 18, the posture angles θ_(bm), θ_(am), and θ_(bk) arecaptured as the posture data in this posture and stored in the storagesection, not depicted, in the calibration value computing section 153(S260).

Here, if it is assumed that the calibration parameters of the boom 4 andthe arm 5 computed in S240 are θ^(set) _(bm) and θ^(set) _(am), theheight of the reference point B in the front implement coordinate systemis given by the following Equation (12).[Equation 12]z _(set) =L _(bm) sin(θ_(bm)−θ_(bm) ^(set))+L _(am) sin(θ_(am)−θ_(am)^(set))+L _(bk) sin(θ_(bk)−θ_(bk) ^(s))   (12)

Next, it is determined whether to end posture data acquisition (StepS270). In a case in which a determination result of Step S270 is NO,processes of Steps S250 and S260 are repeated. Furthermore, in a case inwhich the determination result of Step S270 is YES, then simultaneousequations related to Equation (12) are set up using the obtained postureangles θ_(bm), θ_(am), and θ_(bk), the calibration parameter θ^(s) _(bk)is computed and stored in the calibration value computing section 153, acomputation result is output to the work position computing section 154(Step S280), and the process is ended.

While the calibration parameter θ^(s) _(bk) can be computed byperforming the processes in Steps S250 and S260 equal to or larger thanone time, it is possible to enhance the precision of the calibrationparameter θ^(s) _(bk) by changing the posture of the bucket 6 andacquiring a plurality of posture angles θ_(bk) as depicted in, forexample, FIGS. 16 to 19. It is noted that FIGS. 16 to 19 depict only thebucket 6 in the posture in which the claw tip (reference point B) isadapted to the reference plane and do not depict the otherconfigurations such as the arm 5.

The other configurations are similar to those in Embodiment 1.

Embodiment 3 configured as described above can obtain similar effects tothose of Embodiment 1.

Furthermore, while the calibration parameters of the boom 4, the arm 5,and the bucket 6 are simultaneously calculated in Embodiment 1, it isimpossible to strictly suit sensor offsets of the inertial measurementunits 14 to 16 (calibration parameters θ^(s) _(bm), θ^(s) _(am), andθ^(s) _(bk)). For example, it is conceivable that a change L_(bk) sinθ_(bk) in the height of the claw tip position (reference point B) by thesensor offset (calibration parameter θ^(s) _(bk)) of the bucket 6 iscanceled by an amount of change L_(bm) sin θ^(s) _(bm)+L_(am) sin θ^(s)_(am) in the height of the claw tip position (reference point B) by thesensor offsets (calibration parameters θ^(s) _(bm) and θ^(s) _(am)) ofthe boom 4 and the arm 5. Such a phenomenon possibly causes a reductionin estimation precision of the position of the reference point of thework tool in the posture of the front implement 1 that is not adopted atthe time of acquiring the posture angles θ_(bm), θ_(am), and θ_(bk).

Embodiment 3 is made in the light of the above phenomenon inEmbodiment 1. In other words, Equation (11) includes only thecalibration parameters θ^(s) _(bm) and θ^(s) _(am) of the boom 4 and thearm 5 as unknown variables, and the posture angle of the bucket 6 can bemade constant to θ^(end) _(bk). Therefore, it is difficult to includethe influence of the sensor offset (calibration parameter θ^(s) _(bk))of the bucket 6 in the sensor offset (calibration parameter θ^(s) _(bm))of the boom 4 and the sensor offset (calibration parameter θ^(s) _(am))of the arm 5 unlike Embodiment 1, and it is possible to suppress thereduction in the estimation precision of the position of the referencepoint of the work tool in the posture of the front implement 1 that isnot adopted at the time of acquiring the posture angles θ_(bm), θ_(am),and θ_(bk).

Embodiment 4

Embodiment 4 will be described with reference to FIGS. 20 to 25.

In Embodiment 4, a posture angle is acquired in a posture in which eachof coupling portions of coupling the plurality of driven members 4 to 6configuring the front implement 1 and the reference point (or the plumbbob that is the reference point relative index provided at any of thecoupling portions or the reference point) matches the reference plane,and each calibration parameter is computed, whereby the influence of thesensor offsets of the other driven members is mitigated and theprecision of the calibration parameters is enhanced.

FIG. 20 is a flowchart depicting the posture computation process inEmbodiment 4. In addition, FIGS. 21 to 23 are diagrams each depicting aposture in which each of the coupling portions of coupling the drivenmembers and the reference point matches the reference plane. FIG. 21 isa diagram depicting a posture in which a boom tip end matches thereference plane, FIG. 22 is a diagram depicting a posture in which anarm tip end matches the reference plane, and FIG. 23 is a diagramdepicting a posture in which the bucket tip end matches the referenceplane.

In Embodiment 4, the laser emitter 21 is provided at the position of theheight of the boom foot pin and the laser beam 21 a extending in thehorizontal direction with respect to the height of the boom foot pin isassumed as the reference plane.

In FIG. 20, first, adapting the tip end of the boom 4 (coupling portionof coupling the boom 4 and the arm 5) to the reference plane (refer toFIG. 21) and operating the computation posture setting section 18, theposture angle θ_(bm) is captured as posture data in this posture andstored in the storage section, not depicted, in the calibration valuecomputing section 153 (Step S310). At this time, a height z_(a) of thetip end of the boom 4 in the front implement coordinate system is givenby the following Equation (13).[Equation 13]z _(a) =L _(bm) sin(θ_(bm)−θ^(s) _(bm))   (13)

Since the height of the reference plane is identical to the height ofthe origin O of the front implement coordinate system, z_(a)=0 (zero).

Next, it is determined whether to end posture data acquisition (StepS320). In a case in which a determination result of Step S320 is NO,then the posture of the boom 4 is changed to another posture in whichposture data is not acquired yet (Step S311), and the process in StepS310 is repeated. In a case of adapting the tip end of the boom 4 to thereference plane, the boom 4 can take only one posture; thus, the posturedata is acquired by providing a plumb bob at a known length on the tipend of the boom 4 and adapting this plumb bob to the reference plane.Needless to say, in this case, a value of z_(a) is adjusted to thelength of the plumb bob.

Furthermore, in a case in which the determination result of Step S320 isYES, then the calibration parameter θ^(s) _(bm) is computed fromEquation (13) using the obtained posture angle θ_(bm) and stored in thecalibration value computing section 153, and a computation result isoutput to the work position computing section 154 (Step S330).

Next, adapting the tip end of the arm 5 (coupling portion of couplingthe arm 5 and the bucket 6) to the reference plane (refer to FIG. 22)and operating the computation posture setting section 18, the postureangle θ_(am) is captured as posture data in this posture and stored inthe storage section, not depicted, in the calibration value computingsection 153 (Step S340). At this time, a height z_(a) of the tip end ofthe arm 5 in the front implement coordinate system is given by thefollowing Equation (14) with the calibration parameter of the boom 4obtained in Step S330 assumed as θ^(set) _(bm).[Equation 14]z _(a) =L _(bm) sin(θ_(bm)−θ_(bm) ^(set))+L _(am) sin(θ_(am)−θ_(am)^(s))   (14)

Next, it is determined whether to end posture data acquisition (StepS350). In a case in which a determination result of Step S350 is NO,then the postures of the boom 4 and the arm 5 are changed to otherpostures in which posture data is not acquired yet (Step S341), and theprocess in Step S340 is repeated. Furthermore, in a case in which thedetermination result of Step S350 is YES, then the calibration parameterθ^(s) _(am) is computed from Equation (13) using the obtained postureangles θ_(bm) and θ_(am) and stored in the calibration value computingsection 153, and a computation result is output to the work positioncomputing section 154 (Step S360).

Next, by adapting the tip end of the bucket 6 (reference point B) to thereference plane (refer to FIG. 23) and operating the computation posturesetting section 18, the posture angles θ_(bm) and θ_(am), and θ_(bk) arecaptured as the posture data in this posture and stored in the storagesection, not depicted, in the calibration value computing section 153(S370). At this time, the height z_(set) of the tip end of the bucket 6(reference point B) in the front implement coordinate system is given byEquation (12) with the calibration parameters of the boom 4 and the arm5 obtained in Steps S330 and S360 assumed as θ^(set) _(bm) and θ^(set)_(am).

Next, it is determined whether to end posture data acquisition (StepS380). In a case in which a determination result of Step S380 is NO,then the posture of the front implement 1 is changed to another posturein which posture data is not acquired yet (Step S371), and the processin Step S370 is repeated. Furthermore, in a case in which thedetermination result of Step S380 is YES, then the calibration parameterθ^(s) _(bk) is computed from Equation (11) using the obtained postureangles θ_(bm), θ_(am), and θ_(bk) and stored in the calibration valuecomputing section 153, and a computation result is output to the workposition computing section 154 (Step S390).

While the calibration parameters θ^(s) _(bm), θ^(s) _(am), and θ^(s)_(bk) can be computed by performing each of the processes in Steps S310,S340, and S370 equal to or larger than one time, it is possible toenhance the precision of the calibration parameters θ^(s) _(bm), θ^(s)_(am), and θ^(s) _(bk) by changing the postures of the driven members 4to 6 and acquiring a plurality of posture angles θ_(bm), θ_(am), andθ_(bk).

The other configurations are similar to those in Embodiment 1.

Embodiment 4 configured as described above can obtain similar effects tothose of Embodiment 1.

Furthermore, while it is conceivable that the influence of aninteraction among the boom 4, the arm 5, and the bucket 6 cannot becompletely mitigated in Embodiment 2, the calibration parameters of theboom 4, the arm 5, and the bucket 6 are computed individually and it is,therefore, possible to expect improvement in posture estimationprecision in a wide range in Embodiment 4.

While the case on the premise that the calibration parameters θ^(s)_(bm), θ^(s) _(am), and θ^(s) _(bk) are given as constant values hasbeen described in Embodiment 4, the hydraulic excavator 100 may beconfigured such that calibration tables indicating a relationshipbetween the detection values of the inertial measurement units 14 to 16and the calibration parameters θ^(s) _(bm), θ^(s) _(am), and θ^(s) _(bk)are created, and the calibration parameters are determined in responseto the detection values of the inertial measurement units 14 to 16, asdepicted in, for example, FIGS. 24 and 25. In other words, in a case inwhich the calibration parameters θ^(s) _(bm), θ^(s) _(am), and θ^(s)_(bk) of the boom 4, the arm 5, and the bucket 6 can be computedindividually as described in Embodiment 4, calibration tables depictedin FIGS. 24 and 25 can be created. Configuring the hydraulic excavator100 as described above makes it possible to expect realization of higherprecision posture estimation. In FIGS. 24 and 25, a plot point denotesthe calibration parameter obtained in each posture. FIG. 24 depicts acase of linearly interpolating the calibration parameter per section,and FIG. 25 depicts a case of smoothing the calibration parameter in allpossible angle sections.

Features of Embodiments 1 to 4 and the modification will next bedescribed.

(1) In Embodiments 1 to 4, a construction machine (for example,hydraulic excavator 100) includes: a multijoint type front workimplement 1 that is configured by coupling a plurality of driven members(for example, a boom, an arm 5, and a bucket 6) including a work tool(for example, the bucket 6) and that is supported by a machine body (forexample, an upper swing structure 2) of the construction machine in sucha manner as to be rotatable in a perpendicular direction; postureinformation sensors (for example, inertial measurement units 14 to 16)that detect posture information about the plurality of driven members;and a front posture computing device (for example, a posture computingdevice 154) that computes a posture of the multijoint type front workimplement on the basis of detection information from the postureinformation sensors, an action of the multijoint type front workimplement being controlled on the basis of the posture of the multijointtype front work implement computed by the front posture computingdevice. The construction machine is configured in such a manner that thefront posture computing device includes: a reference position settingsection (for example, a reference plane setting section 152) that sets areference position (for example, a reference plane) specified relativelyto the machine body; a calibration value computing section 153 thatcomputes calibration parameters used in calibration of the detectioninformation from the posture information sensors; and a work positioncomputing section 154 that computes a relative position of the work toolto the machine body on the basis of the detection information from theposture information sensors and a computation result of the calibrationvalue computing section. Further, the construction machine is configuredin such a manner that the calibration value computing section computesthe calibration parameters on the basis of the detection informationfrom the posture information sensors in a plurality of postures of thefront work implement in which a reference point set on any of theplurality of driven members in advance matches the reference positionset by the reference position setting section, which differ in a postureof at least one of the plurality of driven members, and the number ofwhich corresponds to the number of the driven members.

Configuring the construction machine in this way makes it possible tohighly precisely compute the posture of the work implement with asimpler configuration.

(2) Furthermore, in Embodiments 1 to 4, the construction machineaccording to (1) is configured such that the reference position settingsection sets a reference plane parallel to a horizontal surface as thereference position, and the calibration value computing section computesthe calibration parameters on the basis of the detection informationfrom the posture information sensors in a plurality of postures of thefront work implement in which the reference point set on any of theplurality of driven members in advance matches any of positions on thereference plane, which differ in the posture of at least one of theplurality of driven members, and the number of which corresponds to thenumber of the driven members.

Setting the reference position to the reference plane parallel to thehorizontal surface in this way makes it possible to facilitate adaptingthe reference point of any of the driven members to the referenceposition (reference plane) and to facilitate performing posturecomputation.

(3) Moreover, in Embodiments 1 to 4, the construction machine accordingto (2) includes: a machine body sloping detection section that detects aslope angle of the machine body with respect to the horizontal surface;and a sloping reference plane computing section that computes a slopingreference plane obtained by sloping the reference plane on the basis ofthe slope angle of the machine body detected by the machine body slopingdetection section, is configured such that the calibration valuecomputing section computes the calibration parameters on the basis ofthe detection information from the posture information sensors in aplurality of postures of the front work implement in which the referencepoint set on any of the plurality of driven members in advance matchesany of positions on the sloping reference plane, which differ in theposture of at least one of the plurality of driven members, and thenumber of which corresponds to the number of the driven members.

By so configuring, even in the case of disposing the hydraulic excavator100 on the sloping surface and carrying out work, it is possible tocompute the calibration parameters θ^(s) _(bm), θ^(s) _(am), and θ^(s)_(bk), and to carry out the work by appropriately calculating the clawtip position of the bucket 6 (reference position B) in the frontimplement coordinate system.

(4) Furthermore, in Embodiments 1 to 4, the construction machineaccording to (2) is configured such that the reference position is madeto match a position on the reference plane by causing the referencepoint set on any of the plurality of driven members in advance to matcha reference plane index that visually indicates a position of thereference plane.

It is thereby possible to set the mounting position of the laser emitter21 that emits the laser beam 21 a at an arbitrary height; thus, it ispossible to set the reference plane (laser beam 21 a) at an arbitraryheight. Furthermore, no irregularities are generated on the referenceplane since the laser beam 21 ahas a high ability to travel in astraight line.

(5) Moreover, in Embodiments 1 to 4, the construction machine accordingto (1) is configured such that the calibration value computing sectioncomputes the calibration parameters on the basis of the detectioninformation from the posture information sensors in a plurality ofpostures of the front work implement in which a reference point relativeindex that indicates a position apart from the reference point set onany of the plurality of driven members in advance in a verticallydownward direction matches the reference position, which differ in theposture of at least one of the plurality of driven members, and thenumber of which corresponds to the number of the driven members.

By so configuring, it is possible to compute the calibration parametersθ^(s) _(bm), θ^(s) _(am), and θ^(s) _(bk) more effectively since thefront implement 1 can take more postures by changing the length of theplumb bob 20.

(6) Further, in Embodiments 1 to 4, the construction machine accordingto (1) is configured such that the calibration value computing sectioncreates a calibration parameter table to which the detection informationfrom the posture information sensors is input and which outputs thecalibration parameters that are the computation result of thecalibration value computing section, and that the work positioncomputing section computes relative positions of the plurality of drivenmembers to the machine body on the basis of the detection informationfrom the posture information sensors and on the basis of the calibrationparameters output from the calibration parameter table on the basis ofthe detection information from the posture information sensors.

<Note>

It is noted that the ordinary hydraulic excavator that drives thehydraulic pump by the prime mover such as the engine has been describedin Embodiments 1 to 3 and the modification by way of example. Needlessto say, the present invention can be applied to a hybrid hydraulicexcavator that drives a hydraulic pump by an engine and a motor, amotorized hydraulic excavator that drives a hydraulic pump only by amotor, or the other hydraulic excavator.

Furthermore, the present invention is not limited to Embodiments 1 to 3and the modification but encompasses various modifications andcombinations without departing from the gist of the invention. Moreover,the present invention is not limited to the work machine that includesall the configurations described in Embodiments 1 to 3 and themodification but encompasses those from which a part of theconfigurations is deleted. Furthermore, the configurations, thefunctions, and the like described above may be realized by, for example,designing a part or all thereof with integrated circuits. Moreover, theconfigurations, functions, and the like described above may be realizedby software by causing a processor to interpret and execute programsthat realize the respective functions.

REFERENCE SIGNS LIST

-   1 front implement (front work implement)-   2 upper swing structure-   2 a swing motor-   3 lower travel structure-   3 a travel motor-   4 boom-   4 a boom cylinder-   5 arm-   5 a arm cylinder-   6 bucket-   6 a bucket cylinder-   7 hydraulic pump device-   8 control valve-   9 cabin-   9 a, 9 b operation lever (operation device)-   12 inertial measurement unit-   14 boom inertial measurement unit-   15 arm inertial measurement unit-   15 a, 15A posture computing device-   15 b monitor display control system-   15 c hydraulic system control system-   15 d work execution target surface computing device-   16 bucket inertial unit-   17 work execution information-   18 computation posture setting section-   19 controller-   20, 22 plumb bob-   21 laser emitter-   21 a laser beam-   23 leveling line-   23 a, 23 b reference member-   100 hydraulic excavator-   151, 151 a design information storage section-   152 reference plane setting section-   153 calibration value computing section-   154 work position computing section

The invention claimed is:
 1. A construction machine comprising: amultijoint type front work implement that is configured by coupling aplurality of driven members including a work tool and that is supportedby a machine body of the construction machine in such a manner as to berotatable in a perpendicular direction; posture information sensors thatdetect posture information about the plurality of driven members; and afront posture computing device that computes a posture of the multijointtype front work implement on the basis of detection information from theposture information sensors, an action of the multijoint type front workimplement being controlled on the basis of the posture of the front workimplement computed by the front posture computing device, wherein thefront posture computing device includes a reference position settingsection that sets a reference position specified relatively to themachine body; a calibration value computing section that computescalibration parameters used in calibration of the detection informationfrom the posture information sensors; and a work position computingsection that computes a relative position of the work tool to themachine body on the basis of the detection information from the postureinformation sensors and a computation result of the calibration valuecomputing section, and the calibration value computing section computesthe calibration parameters on the basis of the detection informationfrom the posture information sensors in a plurality of postures of thefront work implement in which a reference point set on any of theplurality of driven members in advance matches the reference positionset by the reference position setting section, which differ in a postureof at least one of the plurality of driven members, and the number ofwhich corresponds to the number of the driven members.
 2. Theconstruction machine according to claim 1, wherein the referenceposition setting section sets a reference plane parallel to a horizontalsurface as the reference position, and the calibration value computingsection computes the calibration parameters on the basis of thedetection information from the posture information sensors in aplurality of postures of the front work implement in which the referencepoint set on any of the plurality of driven members in advance matchesany of positions on the reference plane, which differ in the posture ofat least one of the plurality of driven members, and the number of whichcorresponds to the number of the driven members.
 3. The constructionmachine according to claim 2, including: a machine body slopingdetection section that detects a slope angle of the machine body withrespect to the horizontal surface; and a sloping reference planecomputing section that computes a sloping reference plane obtained bysloping the reference plane on the basis of the slope angle of themachine body detected by the machine body sloping detection section,wherein the calibration value computing section computes the calibrationparameters on the basis of the detection information from the postureinformation sensors in a plurality of postures of the front workimplement in which the reference point set on any of the plurality ofdriven members in advance matches any of positions on the slopingreference plane, which differ in the posture of at least one of theplurality of driven members, and the number of which corresponds to thenumber of the driven members.
 4. The construction machine according toclaim 2, wherein the reference position is made to match a position onthe reference plane by causing the reference point set on any of theplurality of driven members in advance to match a reference plane indexthat visually indicates a position of the reference plane.
 5. Theconstruction machine according to claim 1, wherein the calibration valuecomputing section computes the calibration parameters on the basis ofthe detection information from the posture information sensors in aplurality of postures of the front work implement in which a referencepoint relative index that indicates a position apart from the referencepoint set on any of the plurality of driven members in advance in avertically downward direction matches the reference position, whichdiffer in the posture of at least one of the plurality of drivenmembers, and the number of which corresponds to the number of the drivenmembers.
 6. The construction machine according to claim 1, wherein thecalibration value computing section creates a calibration parametertable to which the detection information from the posture informationsensors is input and which outputs the calibration parameters that arethe computation result of the calibration value computing section, andthe work position computing section computes relative positions of theplurality of driven members to the machine body on the basis of thedetection information from the posture information sensors and on thebasis of the calibration parameters output from the calibrationparameter table on the basis of the detection information from theposture information sensors.